rqt_console is a ROS tool that displays a user interface for listening to ROS logging and error messages. rqt_console is useful for viewing Baxter's software/hardware INFO/WARNING/ERROR/DEBUG message coming from Baxter's software stack.
$ sudo apt-get install ros-indigo-rqt-console
$ sudo apt-get install ros-hydro-rqt-console
$ sudo apt-get install ros-groovy-rqt-console
From a properly initialized Baxter ROS environment, run the command:
$ rosrun rqt_console rqt_console
This will bring up the rqt_console interface and immediately start displaying log messages. You can filter using the pattern matching rules at the bottom.
Note: If there is a flood of error messages, as can happen when there is an actual hardware error, rqt_console has a tendency to easily get overrun and come to a stand-still. This is why it is often useful to hit 'Pause' on rqt_console as soon as it comes up, then select your desired filter options.
For more information see the ROS rqt_console wiki.